Water & salt: resetting estimations
This paper reviewed the historical forecasting of CSG water production in Queensland leading up to the development and operation of the CSG to LNG export industry, and compare that to the current actual produced volumes now that the projects have come on stream.
This is then contrasted with a similar sequence of forecasting and production in the US where the industry is now in declining production. Current estimates of water and salt production in Queensland are about 25% those made by government and academia prior to the expansion of CSG to LNG export and ~70% of the 2010-11 industry estimates. This discrepancy was similarly observed in the US and we show that it can be attributable to a combination of the following factors:
- Gas industry conservatism driven by the bias to reduce project risk and achieve gas delivery targets
- Government conservatism driven by a bias for prudent forecasting i.e. to assure that a credible worst case can still be managed within the regulatory framework
- Academia conservatism driven by a bias for understanding worse case scenarios of environmental impact
- The use of numerical models for basin scale impact assessment that do not take account of near-well multi-phase flow characteristics of saturation and relative permeability
- A systemic underestimation of the cumulative effects on depressurisation of the coal resource where one operator’s asset requires less water production to reach target reservoir pressures due to neighbouring operator production. This is mainly because each operator only has access to its own development plans
HIGHLIGHTS
- CSG in Qld is transitioning from ∼315 PJ/yr for domestic use to ∼1500 PJ/yr by 2019 driven by LNG export
- Pre-production forecasts of peak produced water volumes have ranged from 120 to 300 GL/y
- Current water production is ∼60.5 GL/yr with a history matched forecast peak of 70–80 GL/yr
- Production is 25% of government and academia estimates and ∼70% of 2010-11 industry estimates
- There has been underestimation of cumulative effects on depressurization from multiple assets
PROJECT OUTPUT
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Underschultz JR, Vink S, Garnett A (2018), Coal seam gas associated water production in Queensland: Actual vs predicted, Journal of Natural Gas Science and Engineering, April 2018, vol 52, pp 410-422.
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